Physics - Term 4 - Week 10

An electric circuit is a closed loop that allows current to flow from a power source, through components, and back to the source. The basic components of a circuit include a voltage source (like a battery), conductors (wires), and loads (like resistors or light bulbs). Understanding how these components interact is crucial for analyzing circuit behavior.

Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. This relationship can be expressed with the formula V = I × R. This law is fundamental in calculating how much current will flow in a circuit given a certain voltage and resistance.

In a series circuit, components are connected end-to-end, so the same current flows through each component. The total resistance in a series circuit is the sum of the individual resistances. In contrast, in a parallel circuit, components are connected across the same voltage source, and the total resistance is found using the formula 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn. Understanding these configurations is essential for circuit analysis.

Suppose we have a circuit with a 12V battery and a resistor of 4Ω. To find the current flowing through the circuit, we use Ohm's Law: I = V/R. Substituting the values, we get I = 12V / 4Ω = 3A. Therefore, the current flowing through the circuit is 3 amperes.

Consider a series circuit with three resistors: R1 = 2Ω, R2 = 3Ω, and R3 = 5Ω. The total resistance (R_total) is calculated as R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω. This means the total resistance in the circuit is 10 ohms.

For a parallel circuit with two resistors, R1 = 6Ω and R2 = 3Ω, we calculate the total resistance using the formula 1/R_total = 1/R1 + 1/R2. This gives us 1/R_total = 1/6 + 1/3 = 1/6 + 2/6 = 3/6. Therefore, R_total = 6/3 = 2Ω. The total resistance in this parallel circuit is 2 ohms.

Let's work through a problem together. A circuit has a voltage of 24V and a resistor of 8Ω. What is the current flowing through the circuit? Using Ohm's Law, we find I = V/R = 24V / 8Ω = 3A. Now, try to solve a similar problem with a voltage of 30V and a resistor of 10Ω.

In a series circuit with two resistors, R1 = 4Ω and R2 = 6Ω, what is the total resistance? We add the resistances: R_total = R1 + R2 = 4Ω + 6Ω = 10Ω. Now, let's calculate the total resistance if we add a third resistor of 5Ω.

Consider a parallel circuit with three resistors: R1 = 12Ω, R2 = 4Ω, and R3 = 6Ω. To find the total resistance, we use the formula 1/R_total = 1/R1 + 1/R2 + 1/R3. Let's calculate this step by step together.

Solve the following problems independently: 1) A circuit has a voltage of 48V and a resistance of 12Ω. What is the current? 2) If the current is 2A and the resistance is 6Ω, what is the voltage? Show your calculations.

Calculate the total resistance in a series circuit with resistors of 3Ω, 5Ω, and 7Ω. What is the total resistance? Write down your steps and the final answer.

For a parallel circuit with resistors of 10Ω and 20Ω, calculate the total resistance. Use the formula for parallel resistances and show your work.

• V = I × R
• R = V / I
• I = V + R
• V = R / I

Answer: V = I × R

Ohm's Law states that voltage equals current multiplied by resistance.

• R_total = R1 + R2 + ...
• R_total = 1/R1 + 1/R2
• R_total = R1 × R2
• R_total = R1 - R2

Answer: R_total = R1 + R2 + ...

In a series circuit, the total resistance is the sum of all individual resistances.

• It increases
• It decreases
• It stays the same
• It doubles

Answer: It decreases

Adding more resistors in parallel decreases the total resistance.

Answer: 4A

Using Ohm's Law, I = V/R = 36V / 9Ω = 4A.

Answer: 15Ω

In a series circuit, R_total = R1 + R2 = 5Ω + 10Ω = 15Ω.

• 8Ω
• 6Ω
• 12Ω
• 4Ω

Answer: 8Ω

Using Ohm's Law, R = V/I = 24V / 3A = 8Ω.

• Current is the same through all components
• Voltage is the same across all components
• Total resistance is the sum of resistances
• All components must be identical

Answer: Voltage is the same across all components

In parallel circuits, the voltage across each component is the same.